The molecular characterization of neural cell surface antigens during development may give some clue as to their importance for cell recognition and interaction in the nervous system. Cell type specific antigens will be characterized as to their molecular nature. Their differential distribution on particular cell types will be determined using cell biological and immunohistological methods. Cell surface antigen expression will be analyzed at different developmental stages and their functional significance be probed for. Cell type specific antibodies will be used to separate cerebellar cells and cell hybrids using a fluorescence activated cell sorter and affinity chromatography with antibody columns.